.sidebar {
    position: fixed;
    top: 0;
    bottom: 0;
    left: 0;
    z-index: 100; /* Behind the navbar */
    padding: 0;
    font-size: 15px;
    box-shadow: inset -1px 0 0 rgba(0, 0, 0, .1);
    overflow-y: auto;
}